The introduction of surgical simulation on three-dimensional-printed models in the cardiac surgery curriculum: an experimental project

Aims Training in congenital cardiac surgery has become more and more difficult because of the reduced opportunities for trainees in the operating room and the high patient anatomical variability. The aim of this study was to perform a pilot evaluation of surgical simulation on a simple 3D-printed heart model in training of young surgeons and its potential inclusion in the curriculum of residency programs. Methods A group of 11 residents performed a surgical correction of aortic coarctation using a 3D-printed surgical model. After teaching the surgical procedure, a simulation was performed twice, at different times, and was evaluated quantitatively and qualitatively by a senior surgeon. A 3D model-based training program was then developed and incorporated into our cardiac surgery training program. Results A significant improvement in surgical technique was observed between the first and second surgical simulations: median of 65% [interquartile range (IQR) = 61–70%] vs. 83% (IQR = 82–91%, P < 0.001). The median time required to run the simulation was significantly shorter during the second simulation: 39 min (IQR = 33–40) vs. 45 min (IQR = 37–48; P = 0.02). Regarding the simulation program, a basic and an advanced program were developed, including a total of 40 different simulated procedures divided into 12 sessions. Conclusion Surgical simulation using 3D-printing technology can be an extremely valuable tool to improve surgical training in congenital heart disease. Our pilot study can represent the first step towards the creation of an integrated training system on 3D-printed models of congenital and acquired heart diseases in other Italian residency programs.


Introduction
Training in cardiac surgery has always been challenging because of the limited possibilities for trainee surgeons to practice in the operating room, the high specialization required, and the high risk to patient safety. 1 Congenital heart surgeons may require even more training, primarily because of the rarity of the disorders and the high variability between defects and patients with the same disease. 2,3 recent years, 3D cardiac segmentation and reconstruction of the patient's heart have emerged as interesting innovative tools.This technology is mainly based on the utilization and analysis of standard 2D cross-sectional imaging [such as computerized tomography (CT) scan or cardiac MRI], which are used to reconstruct a 3D model.5][6][7] 3D anatomy and the spatial relationship between cardiac structures have particular value for the understanding of congenital cardiac malformations. 8,9 the last 5 years, 3D models have played an increasingly important role in our center in the surgical planning for treating complex congenital heart disease or to anticipate a minimally invasive approach in simple disease. 10All models have been printed using a transparent plastic resin, which allows the manipulation of cardiac structures and analysis of the external and internal anatomical features of each individual cardiac anatomy.More recently, the introduction of a new elastic resin material has enabled the production of 3D-printed hearts that can be manipulated, cut, and sutured. 11This led to the simulation of surgical maneuvers that can be reproduced prior to the surgical procedure that will be performed in the operating room. 12ased on this experience, we decided to introduce the use of surgical simulation in the training curriculum of the cardiac surgery residents of our center.Our goal was to allow young surgeons to practice cardiac procedures in a safe environment as often as they wish, and to improve their knowledge and skills.
The aim of this study was to evaluate the effectiveness of surgical simulation on 3D-printed heart models by validating the surgical simulation on a pilot model of aortic coarctectomy performed by our residents.The second goal was to plan a consistent and reproducible simulation training program to be incorporated into our residency program.If proven to be effective, this could then be proposed as part of the curriculum of other Italian cardiac surgery training programs.

Methods
The cardiac surgical simulator In 2021, a surgical simulator called 'TrainHeart' (deposit number IT102021000031058) was developed and patented under the aegis of the University of Padua with the aim of reproducing the operating field and the position of the surgeon and the different surgical accesses for the treatment of congenital and acquired heart disease.
The surgical simulator was designed using Shapr3D (Siemens, Parasolid, Budapest, Hungary).This is composed of a static item and a mobile plate.The first part is a semicircular structure with an opening in the upper part to reproduce a sternotomy access (5 Â 7 cm).The plate is used to insert the 3D-printed models into the simulator.A row of LED lights is placed inside the simulator on both sides where the heart is positioned to shed light on the operating field.All the elements that compose the simulator were 3D printed using the Sisma Everes Uno 3D printer (SISMA, Vicenza, VI, Italy) and solid resins (SISMA) (Fig. 1).To reproduce different surgical approaches of minimally invasive accesses, we have also developed three different types of covers (for mini-sternotomy inferior/superior, right lateral thoracotomy and left lateral thoracotomy, all with an opening of 3 Â 5 cm).These covers were printed in elastic resin (SISMA) using the same printer as mentioned above, thus allowing the cover to be inserted on top of our simulator (Figure S1, http://links.lww.com/JCM/A614).

Validation of the program
A total of 11 cardiac surgery residents (including 3 residents in the first year of surgical training, 4 in the second, and 4 in the third year) were enrolled in the study.Residents were provided with a video showing the surgical correction of the aortic coarctation on the 3D-printed model performed by a cardiac surgeon with over 20 years of experience (V.V.) (Fig. 2, Video 1, http://links.lww.com/JCM/A626).After giving them 24 h to watch the video and familiarize themselves with the procedure, they were asked to perform the procedure on the model while recording and timing their performance.The video was then reviewed by the staff surgeon (V.V.) and discussed with the resident, explaining any incorrect procedure.A week later, the residents were asked to repeat the surgery simulation again on the 3D-printed model.Again, the recording was examined by the staff surgeon and then reviewed with each resident (Fig. 3).
Three-dimensional heart models for surgical simulation Over the last few years, a library of cardiac images from CT, MRI and 2D ultrasound of patients with congenital and acquired heart malformations was created, covering almost the entire spectrum of congenital cardiac malformations.
The models were obtained from a CT acquisition of patients undergoing surgical correction at our institution.They were then reconstructed using the Mimics InPrint software (Materialise, Leuven, Belgium), which allowed an STL model to be obtained.Each model was then modified using Meshmixer (Autodesk Inc, San Rafael, California, USA), thus reproducing the patient's heart.Finally, the 3D models were printed using the Sisma Everes Uno 3D printer (SISMA) and a specific elastic resin (SISMA), which allows flexible models to be obtained.The cost of every single 3D model differs according to the size but is approximately 30 euros.

Training program development
After validating the feasibility and effectiveness of simulation in the 3D-printed model of aortic coarctation, we sought to validate other 3D-printed models to establish a consistent simulation training process.The final goal was to incorporate it into our residency program and create a more efficient system for our young trainees. 13e training program included a monthly simulation session (with a mean duration of 3 h), and the participation was extended to all cardiac surgery residents in our center.To host the various training sessions, a room dedicated to surgical simulation was used, equipped with a large screen for viewing the operation during the simulation and five different stations, all complete with the simulator, a computer station, and video camera to record the procedure.
The simulation program was created and composed of 12 different simulation sessions in order to cover all the basic cardiac surgical procedures and the most common interventions (Table 1).For each procedure, a technical evaluation table was developed with a score to evaluate performance and to monitor the improvement over time.Each resident was provided with a complete simulation kit consisting of a simulator (TrainHeart) completed by the various covers, a set of surgical instruments, various sutures, and the 3D-printed model for the simulation (different each time).

Design of the resident performance evaluation tools
The surgical simulation of residents was evaluated both quantitatively and qualitatively.The time to complete the correction on the model was first evaluated by comparing the first and second simulations.To carry out a qualitative assessment of the performance, an evaluation table was created by dividing the operation into four parts.Each part included several surgical phases and for each of them, a score from 1 to 5 was assigned according to the accuracy with which it was performed (Table S1, http://links.lww.com/JCM/A614).The scores assigned to each step were then added together to obtain a total score, which was expressed as a percentage of a total of 130 points.

Statistical analysis
The time to perform the surgical simulation and the evaluation of the performance were expressed in terms of median and interquartile range (IQR).A Wilcoxon signed-rank test was performed to compare the score obtained by the residents in two attempts, and the P-value for statistical significance was set at 0.05.Statistical analyses were performed using STATA version 15.1 (Stata Corp LLC, College Station, Texas, USA).

Results
Validation of the simulation on aortic coarctation three-dimensional printed model All surgical residents successfully completed the surgical simulations.The time to complete the second simulation was shorter than the initial one (a median time of 39 min, Surgical simulation on 3D-printed models Cattapan et al. 167  2. The quality of surgical performance improved in 10 of 11 residents (91%) (Table 2).The median percentage score from the simulation assessment was higher during the second simulation (83%, IQR: 82-91%) than during the initial simulation (65%, IQR: 61-70%; P < 0.001) demonstrating an improvement in technical performance.only with repeated procedures. 14This is generally not possible in the operating room because of the limited possibilities available to young surgeons.The ability to practice outside the operating room can improve surgical technique and enhance the learning of residents in a cardiac surgery training program. 15rgical simulation has already been shown to improve education in acquired cardiac surgery procedures.Different types of simulators are available, mainly for cardiopulmonary bypass, coronary artery bypass, and mitral valve surgery. 16However, these models are usually expensive and dedicated to a single disease or procedure, thus reducing the widespread use of the products.

Training program development
Due to the high variability of congenital heart disease, tailored models are needed to possibly reproduce all the different anatomies encountered during surgical practice. 17For this reason, 3D-printed heart models can be a valuable tool to enrich the training program for congenital heart surgeons. 18 this study, we sought to demonstrate how surgical simulation on 3D-printed cardiac models can help improve the surgical skills of young surgeons.The second objective of the study was to establish a consistent and reproducible simulation training program that could be incorporated permanently into our residency program and then potentially exported to other Italian cardiac surgery programs.
First of all, we developed a surgical simulator that was easy to use and with the possibility of recreating different operative accesses.Subsequently, we created an easily accessible library of 3D-printed cardiac models (including both congenital and acquired cardiac anatomies) to be used for surgical simulation and from which we chose an aortic coarctation model for our study.
In this preliminary study, we demonstrated that training in congenital heart surgery using 3D-printed simulation-based training can improve surgical practice, both reducing the time required to perform simulation and increasing the overall performance.
As a consequence, we have developed a training program for cardiac surgery residents to increase exposure to the surgical practice and possibly improve surgical skills.First, a review of the basic surgical techniques was performed.Then, the main acquired and congenital cardiac procedures were analyzed.Our 3D-printed models enable high anatomical fidelity and can reproduce a wide range of disorders and procedures to enhance the surgical practice of young surgeons.The simulation program developed in this study is highly reproducible and with low production costs, allowing large-scale use of the products.
In this study, we demonstrated the possibility of introducing 3D-printing-based surgical simulation in our training program and potentially in other Italian centers.The introduction of surgical simulation as part of the educational curriculum for young cardiac surgeons allows the new generation to practice in a safe environment, review the operation steps as many times as they wish, without risk to the patients, and prepare the trainers for the management of adversity events.

Conclusion
An effective and reproducible model of surgical training on 3D-printed models was proposed and designed.This was validated on a 3D model of aortic coarctation that was used by a group of residents to reproduce a surgical correction.The trainees showed an improvement in both time and quality.This pilot model can be the first step towards creating an integrated educational system of surgical training on 3D-printed models of congenital and acquired cardiac diseases in other Italian residency programs.

1 . 1 .
Tissue dissection (25 points maximum) Is the transection clear (i.e not jagged)?Is the pulmonary portion reinforced with a stitch)?Is there enough diatance on both ends of the transected PDA?Is the PDA transection perpendicular to the vessel?Is the distal PDA suture a safe distance from the aorta (1-2 mm)?Is proximal the PDA suture a safe distance from the left pulmonary artery (1-2 mm)?Distal ligation Proximal ligation Has the descending aorta been dissected?Has the PDA been dissected?Has the proximal portion of the aortic arch been dissected?Has the subclavian artery been dissected?Has the isthmus been dissected?Tissue dissection (25 points maximum) Is the transection clear (i.e not jagged)?Is the pulmonary portion reinforced with a stitch)?Is there enough diatance on both ends of the transected PDA?Is the PDA transection perpendicular to the vessel?Is the distal PDA suture a safe distance from the aorta (1-2 mm)?Is proximal the PDA suture a safe distance from the left pulmonary artery (1-2 mm)?Distal ligation Proximal ligation Has the descending aorta been dissected?Has the PDA been dissected?Has the proximal portion of the aortic arch been dissected?Has the subclavian artery been dissected?Has the isthmus been dissected?Flowchart of the study.developed: a 'basic simulation program' dedicated to residents in their first and second year of training, and an 'advanced simulation program' for surgical residents in the remaining 3 years.The 'basic simulation program' has been designed to cover basic cardiac surgical techniques in preparation for the 'advanced program' where residents can simulate the correction of the most common procedures in both acquired and congenital heart disease.Discussion Training in cardiac surgery and in congenital heart surgery requires enormous technical skills, which are acquired 170 Journal of Cardiovascular Medicine 2024, Vol 25 No 2
A total of 40 procedures were identified and a monthly training program (12 sessions/year) was developed (Table 1).Two different types of programs have been 168 Journal of Cardiovascular Medicine 2024, Vol 25 No 2

Table 1
Surgical simulation training program (University of Padua) LimitationsThis study has several limitations.First, we ran the evaluation test on a single 3D-printed model and, second, we evaluated the training model on just 11 cardiac surgery residents at a single institution.The ability to add several Surgical simulation on 3D-printed models Cattapan et al. 171Table2Qualitative and quantitative evaluation of Simulations 1 and 2 3D-printed models and further evaluations may perhaps help validate and increase the effectiveness of this training opportunity for cardiac surgery residents. more